A fuel tank system has been known in which a lid disposed in a fuel tank is opened by turning on a fuel supply switch at the time of fuel supply.
In this type of fuel tank system, a technical idea has been proposed in which an ECU measures a time period in which a signal has been outputted from the fuel supply switch with the fuel supply switch ON, and when the measured time is longer than a preset time, the fuel supply switch is determined to have an abnormality (for example, see Japanese Unexamined Patent Application Publication No. 2003-2399).